The Study On Metallogenic Fluid And Mechanism Of Siding Lead Zinc Ore Field,Guangxi

Siding ore field is located in the complex part of the Jiangnan ground axis,the new Huaxia system and the Guangxi mountain type structure of the spinalcolumn and the Nanling EW tectonic zone,which near the splice site of South China paraplatform Guizhong depression-Luocheng fold belt,belong to the northern Guangxi metallogenic region Rong'an polymetallic metallogenic sub region.It is one of the typical MVT(Mississippi-Valley-type)type lead-zinc deposits in northern Guangxi.For relatively less studies on characteristics,origin of ore-forming fluid and ore-forming mode with different types,this study is based on previous works,the fluid inclusions,ore-forming fluid characteristics,main trace elements and material sources of the calcite in different ore bodies in Siding mining area during the same metallogenic epoch are discussed further.The main achievements and conclusion are summarized as follows:(1)The ore body types can be divided into two types:the steep inclined vein and the nest mineral body on the surface to the elevation 290.Located below the 290 elevation,the base Cambrian is a quasi-layered,lenticular ore body.(2)The metallogenic process of the deposits in Siding orefield can be divided into four metallogenic stages,which are sphalerite stage;sphalerite galena pyrite calcite stage;galena calcite stage;sphalerite calcite stage.(3)In the field,the ore-forming fluid of steep inclined vein and the nest mineral body is mainly medium-low temperature,with temperature range from 84.3-117.6?,while the ore-forming fluid of quasi-layered,lenticular ore body is mainly medium-low temperature,with temperature range from 98.1-239.1 ?.In addition,both the salnity and density are low.From the early stage to late stage,the density of ore-forming fluid increase with the decrease of temperature.(4)Two different types of ore bodies may be formed in the same metallogenic stage in the same metallogenic epoch,and the source of ore forming minerals is different.The steeply inclined vein and nesting ore bodies are mainly derived from the original ore bearing fluids.The layered and lenticular ore bodies are mainly precipitated by carbonate leaching from the hot brine.(5)The results of electron probe test show that the content of Fe elements in sphalerite shows that the formation temperature of steeply dipping vein orebody is lower and oxygen fugacity is higher;the formation temperature is high,oxygen fugacity is low,and the oxygen fugacity is relatively stable.The Pb/S value in galena reflects that the sulfur fugacity has changed to varying degrees in the mineralization process.The S/Fe value of pyrite shows that the layered ore bodies are characterized by sedimentary characteristics and hydrothermal pyrites,while the steeply inclined orebodies are hydrothermal.(6)With the comprehensive study of Siding orefield,the metallogenic model has been established,which can provide a reference for the next step prospecting.